I'm not trying to counter the argument, I'm saying there's two options
option A we do have free will
option B we are entirely pre-constructed
If A is correct, my own assertion of the situation makes a tremendous difference, and if B is correct it makes no difference.
Ergo the only correct assumption of the situation is that A is correct, and act accordingly, since if B is correct, it doesn't matter anyways,
and if A is correct, my own feelings might change a terrible situation, or give me the energy to stop bad behaviour, since said bad behaviour is not predestined to be mine, just more likely. I'm really not seeing the issue with the concept here.
There are scientific arguments that speak for both sides, and yes a lot is pre-programmed through education, environment and genetics, that much is clear, but one should not assume that all is pre-programmed, since if option A is correct, we would be putting ourselves in the situation "I'm genetically doomed to be a drug addict", and never do anything about it, because it just "has to be like this"
It gives yourself an option to say "yes, I'm a drug addict, and there's nothing anyone could do to stop it, because it is 'destiny'."
I'm not saying he's wrong, in fact he's probably right, a lot is most definitely preprogrammed, I'm just saying that maintaining said point of view can only have a negative effect on your life as far as decisions go.